Electrolytic cell.



D. S. HARTSHORN n A. A. CLAFLIN. ELECTROLYTIG om..

APPLICATION ULBD SEPT. 27, 1910.

Batented Dec. 27, 1910.

W xk -N W-r-NEEEEE lll@ @ATES DERICK S. HARTSHORN, 0F BOSTON, AND ALAN A. CLAFLIN, 0F MEDFORD,

MASSACHUSETTS. l

ELECTROLYTIC CELL.

etages.

Specification of Letters Patent.

Patented Dec. 27, 1.910.

To all whom 'it may concern:

Be it known that we, DERICK S. Haars- HORN and ALAN A. CLAFLIN, citizens of the United States, and residents, respectively, of

Boston, in the county of Suffolk, and 'Med-v ford, in the county of Middlesex, both in the State of Massachusetts, have invented new and useful Improvements in Electrolytic Cells, of which the following isa specification.

The primary object of our present .invention is to facilitate the escape of a gas liberated by electrolysis and thereby to prevent such gas from polarizing the electrode at which it appears and from inducing secondary reactions in the electrolyte by retention therein after its liberation. v .f f

y Our invention may be exemplified by an electrolytie cell arranged for the conversion of potassium chlorid into potassium chlorate. For this purpose we construct an apparatus such as is illustrated in the accompanying drawings, whercin Figure l represents a transverse vertical section of one form of cell; Fig. 2 a longitudinal vertical section of the same cell taken in planes on' lines 2-2 of Fig. 1; Fig. 3 a transverse vertical section of an alternative form of cell; Figli La longitudinal vertical section of the latter Icell taken between the two pairs of sprocket-wheels; and Fig. 5 a detail belonging thereto. 3

In the apparatus' represented by Fig. l and Fig. 2, the main body a of the cell is a rectangular vessel made of or lined with a concreteof hydraulic cement or other chemically resistant material; `and at the top edge of one of its longitudinal sides it has a lateral extension b urving outward and upward through ab ut a quadrant of a cylindrical segment, to which geometrical shape it conforms in its lower portions but flares away therefrom somewhat at its upper parts. The other longitudinal side of the main body of the vessel is made higher than the lower edge of the lateral extension opposite thereto and from. the top of this higher side the *upper edges of the ends-of the vesselare ex-` tended across the ends of the lateral extension to meet the upper edge of the 'same and thus to inclose the space oth-erwise bounded by the cylindrical quadrant.

lThe lower ortion of the interior of the lateral extensionof the cell wliichthere conforms. to a cylindrical segmentis covered.

with a metal plate c of corresponding shape, eitherVV consisting entirely of platinum or having its exposed surface plated with lplatinum .and its edges turned backward and embedded in the cement concrete to prevent corrosion at the junction of the platinum with the cheaper metal upon which it is plated for economic reasons. This platinum plate constitutes the anodeef' the electrolytic cell. Upon the upper edges of the ends of the body of the cell, above the lower edge of its lateral extension, are mounted bearings for a shaft d extending lengthwise ofthe cell and having its axis concentric with the cylindrical segment surface of the platinum anode. This shaft d is made of copper and it carries a cylindrical cage symmetrical thereto, also made of copper and having the circumferential periphery of its drum composed of a series of parallel copper bars c, e, likewise parallel to the shaft and preferably so shaped in cross sect-ion as to have the outermost surface of leach as nearly as practicable a short segment of a -cylinder concentric to the axis of the shaft aroundwhich it is made to revolve; but if sufficiently nume ous these bars can be rectangular in cross-section. A convenient mode of supporting them is by annular rims f, f, at the outer ends of spokes g, g, extending radially from the shaft. These peripheral bars of the cylindrical cage constitute the cathode of the electrolytic cell when brought into close proximity to the platinum anode; and for the most effective work the outermost surface of each when opposed to the exposed surface ofl such'anode should be about one sixteenth of an inch therefrom. A belt-pulley 7L upon one end of the shaft d serves lto rotate the cage and to revolve the series of cathode-barsrin front ofthe anode in the directionindicated by an arrow. A suitable cable z' containing an insulated conductor which has its end securely soldered to the back plate of the .anode and leads from the positive pole of an electric generator serves to supply the electric current to the electrolytic' cell; and another similar conductorj leading from the negative pole of -the same generator and terminating, in an intimate contact c with one of the metal journal-boxes of the shaft d, serves to complete the electric circuit, when the space be- #by the `liquid electrolyte.

'the cylindrical The best position for the stationary electrode is such as to locate the greater part of its area. where the rise of its curvature above a horizontal plane has the lesser increments, so that when the level of the liquid electrolyte in the electrolytic cell reaches high enough to enable the lower part of the circumferential periphery of the rotary electrode to dip below its surface a considerable portion of the stationary electrode will be covered by such liquid; although, of course, as soon as the rotary electrode is Set in motion as intended in a direction from the bottom toward the top of the cylindrical lateral extension of the electrolytic cell, it will weep the liquid electrolyte intowhich it dips, along with it so as to cover an additional surface of the stationary electrode if this extends above the initial level to which the cell was originally filled, and will thus proportionately increase the area of electrolytic l action.

1n order to prevent undue radiation of heat from the external walls of the electrolytic vessel, they are covered with wooden lagging m, m, or other thermally non-conducting material; and for the like purpose the top of the vessel is provided with a heatobstructing cover which may be regulated in size to suit the exigencies of the weather; while independently of such cover, oras a lining to a portion of it, a sheet-metal hood is placed over the revolving cage to confine the spattering of the liquid operated upon.

The method of procedure with this apparatus and its mode of operation when employed for converting pottassium chlorid into potassium chloratc are as follows: An aqueous solution of potassium chlorid, preferably standing at about 18o Baume, and constituting the electrolyte, is at the outset of the process heated to about MCOo Fahrenheit, and for the best results should be maintained as nearly as may be at that temperaf ture during the progress of the electrolysis.

The electrolytic cell hereinbefore described is filled with such solution up to a level at which the circumferential periphery of the cylindrical cage will dip just below its surface; and any diminution of the volume of liquid in the course of the operation is to be compensated for, from time to time, by the addition of a suitable quantity of water. The electric current then turned on and cage set into rotation in a direction which causes Aits cathode copper bars to sweep the electrolyte solution up the incline of the anode platinum plate and there subject it to electrolysis in a thin liquid sheet. By this means the hydrogen liberated at the surfaces of the cathode-bars is assisted to effect an immediate escape, first, by the rapid travel of the bars themselves out of the liquid electrolyte carrying with them the hydrogen bubbles adhering there- Vperature above 180 to; and second, by the agitation of the thin sheet of liquid `itself between the electrodes, caused by the swift passage of the bars through it, and the consequent breaking up of its 'surface tension which would otherwise tend to retard the escape of such hydrogen bubbles as were held in suspension. In order to prevent polarization of the eathodes by any persistent adhesion of hydrogen bubbles thereto, a stationary brush fn may be mounted above the revolving cage in such position as to wipe the surfaces of the peripheral bars. The heat evolved by this electrolysis is under ordinary latmospheric conditions sufficient to maintain the temperature of the electrolyte at the desired point of about 1409 Fahrenheit, in such an electrolytic cell as is hereinabove described when provided with the means specified for preventing undue refrigeration. Indeed, it will sometimes happen that the contents of the cell become too hot and need to be allowed to cool off by removing part or all of the cover which may be made in separate divisions for that purpose; and on the other hand the exposure of the apparat-us to the effects of too severewinter weather may render expedient the application of extraneous heat such as would be supplied by a steam coil within the body of the vessel containing the electrolyte. 1f the temperature of the potassium chlorid solution falls below 950 Fahrenheit the obtainment of potassium chlorate therefrom by this electrolytic process is seriously interfered with by the formation of hypochlorites; and on the other hand, the efficiency of the process is greatly diminished by an increase of tem- Fahrenheit.

For economic working the capacity of the electrolytic cell should be sufiicient to enable the electrolysis to go on uninterruptedly for aconsiderable time, say, an entire day, Without bringing the solution too near the point of saturation with potassium chlorate; for, its increase in quant-ity within the potassium chlorid solution proportionately diminishes the effectiveness of the electrolysis in producing the resulting conversion; At the conclusion of the period set for continuous working, the solution operated upon is allowed to cool; whereupon the potassium chlorate precipitates in crystals and thedepleted liquid is then drawn olf to be enriched with more potassium chlorid ready for further subjection to the same process.

The conversion of potassium chlorid into potassium chlorate by electrolysis is old, and

the chemical transformations by which this,

result is brought about are well understood in the art. 1We have described this process as far as requisite for exemplifying the peculiar construction and mode of operation of our electrolytic cell, which is adapted for use in conducting other electrolysis wherein working-faces arefnear to the surface of the hereinabovedescribed, is 'that-.one of the elective face immersed only just far enough bevcourse, the shape of the face ofthe stationa gas is liberated atone of the electrodes and needs to be eliminated with despatch in such manner as to avoid polarization oit theelectrede-at which it appears and toprevent secondary lreactions zresulting from its further detention Within :the f electrolyte solution.

The fundamental principle Vof our invention vwhen embodied in the most effective mode, asrexemplifiedin the electrolytic cell trodes shall-consist of an extended series of consti-tuent members which, in -continuous succession, are madefto travel into and out of the liquid electrolyte; are brought into operative position in front of the other electrodey of opposite electric lpolarity,.only-when their liquid electrolyte .in which `they rare immersed; and are conveyed thence directly out \of the liquid electrolyte; or in other words, that each component of such traveling electrode shall arrive at its operative position opposite and in vsuitable proximity to the other electrode, with its electrically aclow the surface of the liquid electrolyte to enble this latter to fill the narrow space between the two opposed electrodes, and shall by its onward movement agitate the surface of the liquid electrolyte and without lingering, pass above the same, Obviously, however, the traveling compound electrode need not invariablyconstitute such a cyclic series of bars as to form the circumferential periphery of a rotary cylindrical cage, but might, for example, be arranged like the components of an endless slattcd apron run ning over and moved by suitable rotativel carriers such as sprocket Wheels to bring the several electrode members of the series in continuous succession into a position facing the oppositely electrified electrode vand in close proximity thereto just beneath the surface of the liquid electrolyte and thence di rectly above the same; in which case, of

ary electrode as well as its position would have to conform and be parallel to the path of movement o the components of the traveling electrode.

Such a modified form of apparatus assumed to be put to the same uses as that already described in connection with Figs. 1 and 2, is illustrated by Figs. 3, 4 and 5of the drawings, wherein the body ai of the cell is a. rectangular vessel made of or lined with a concrete of hydraulic cement or other chemically resistant material and externally protected by wooden lagging m, m-"r other non-conductor of heat. Within this cell is a .dat horizontal table bf which with its supports areA made of chemically resistant material,-and which is covered with a metal plate c ot corresponding shape either consisting entirelyv of platinum or having its exposed surface plated with platinum and its edges metalbacking Upon the upper 'edges of -t-he body of' the cell are mounted earings' for shafts fl d', extending lengthwise of the cell and each carrying a pair of sprocket wheels g g. Encompassing these two pairs of sprocket wheels is an endless 2 slatted apron consisting of a continuous series of bars e supported at their ends in `sockets f" 7", which are connected together by alte nately fixed and pivoted links in such manner that each lixed link o rigidly holds a pair ofsockcts in such position that its two.

bars are kept transversely parallel to such tiXed link, while each pivoted link p `fiexibly joins two consecutive pairs of rigidly held sockets. The series of links forms al1-endless chain which while flexible as a whole, maintains thebars of the slatted apron {latwise to their path of travel. The s oc ets thus chained together are spaced apart at distances just right to permitthe sprockets of the sprocket-wheels to tit between them. The shaft of one of thepairs of sprocketwheels is to be provided with a driving pulley outsideof its bearing, and the shaft of the other pair of sprocket-wheels should have its j ournal-boXcs adjustable toward and from those of the driving shaft to enable the endless slatted apron to be made taut enoughto keep it from sagging materially between its rotating supports. These contrivances are too obvious to need delineation in the drawings. lhe bars of the endless slatted apron constitute the cathode of this form of electrolytic cell. They are of copper and sovalso are their sockets and interconnecting links, aswell as the sprocket-wheels, their shafts and journal bearings. A suitable cable z" containing an insulated conductor which has its end securely soldered to the back-plate of the anode and leads from the positive pole of an electric generator, through passages provided for the purpose in the table and its supports,serves to supply the electric current to the electrolytic cell; and another similar conductor j leading from the negative pole of the Same generator and termi-l nating in an intimate contact lc with one 'of ich the metal journalboxes of the driving shaft d -serves to complete the electric circuit, when the space between the bars on the bottom of the endless slatted apron andthe platinum-plate on the top of the table is bridged over by the liquid electrolyte.

Manifestly, the closer together the bars of the traveling electrodes are, the greater' will be the relative area presented for electrolytic activi-ty, but -on the other hand too close proximity-of theseto each other may diminish the facility of escape of the liberated gas between them; and in the particular case of use-for converting potassium chlorid p all cases, of course,

I fectually will into potassium chlorate, the fact that it is desirable to have the total area 'of the electrically active faces of the cathode only about one half of the area of the opposed anode, will serve to determine the distance between the cathode-bars. For other uses, however, it may wellhappen that a relatively greater electrically active area of the traveling electrode will be needed, sufficient even to render it expedient, when employing the form of apparatus wherein the traveling electrode is a rotating cylinder, not to construct its circumferential periphery of separated components. Furthermore, except under such conditions as are presented in the conversion of potassium chlorid into potassium chlorate, the traveling compound electrode in either form of apparatus hereinabove described need not be the cathode of the electrolytic cell. It might constitute the anode, if the electro-chemical conditions caused the gas which required elimination to be vliberated at thatelectrode. And in the constitution ofthe electrodes themselves will have to be suited to the electro-chemical conditions under which they are to operate. Hence, with these explanations it will be seen that our electrolytic cell is adapted to be used for the oxidation byv electrolysis, not only of chlorids into chlorates, but also of chromic salts into chromates, of arsenious salts into arsenates, of ferrous salts into -ferrie salts, and to effect in like manner many other kindred transformations; or even the converse of such reactions by reversing the direction of the electric current to perform reductions of which an example would be furnished in the conversation of nitro-benzol into anilin by liberating oxygen instead of hydrogen. Finally it is to be remarked that the nearer the working faces of the traveling electrode remain to the surface of the liquid electrolyte as they pass along through the latter with a rapidity of movement tending to agitato such surface, the more thoroughly will the surface tension of the liquid electrolyte be broken up, and the more efthe escape of the gas there liberated by electrolysis -be facilitated; so that the efficiency of the apparatus herein described for the purpose of this invention, would diminish in proportion to the depth of immersion of the traveling electrode and would practically disappear as soon as the gas liberated at the working traveling electrode, was by the movement of the latter stirred into the mass of the liquid electrolyte and diffused therein to produce secondary reactions, instead of having its escape therefrom promoted by liberation in close proximity to an agitated surface.

We claim z" l. In an electrolytic cell, two electrodes faces of the of opposite electric polarity, one of which is composed of a series of constituent menibers and is provided with means whereby these members, in continuous succession, are m'ade to dip into the liquid electrolyte from above its level, to travel through the liquid electrolyte only just beneath the surface thereof with a velocity tending to agitato such surface, and thence topass directly out of the liquid electrolyte; while the other electrode is located farther below the surface-of the liquid electrolyte, opposite and in suitable proximity to the traveling electrode where the latter occupies its immersed position.

2. In an electrolytic cell, a movable electrode composed of a series of constituent members and provided with means whereby these members, in continuous succession, are made to dip into the liquid electrolyte from above its level, to travel through the liquid electrolyte only just beneath the surface thereof with a velocity tending to agitate such surface, and thence to pass directly out of the liquid electrolyte, in combination with a stationary electrode of opposite electric polarity, located farther below the surface of the liquid electrolyte in a position opposed and in suitable proximity to an immersed portion of the movable electrode.

3. In an electrolytic cell, a trode composed of a series of constituent members and 'provided with means whereby these members, in continuous succession, Yare made to dip into the liquid electrolyte from above its level, to travel through the liquid electrolyte only just beneath the surface thereof with a velocity tending to agitate such surface, and thence to pass directly out. of the liquid electrolyte, in combination with a stationary electrode plate of opposite electric polarity, located farther below the surface of the liquid electrolyte, in a position parallel to the path of the immersed portion of the movable electrode and in suitable proximity thereto.

e. In an electrolytic cell, a movable electrode composed of a cyclic seriesv of interconnected parallel bars supported partly above and partly belowLthe level. of the| liquid electrolyte and provided with rotative means whereby they are made to travel in continuous succession in an endless course transverse to their'length into and out of the liquid electrolyte, but only to become immersed therein just beneath its surface and to move through the same.with -a velocity tending to\agitate such surface, i`n combination with a stationary electrode plate of opposite electric polarity low the surface of the liquid electrolyte in position parallel to the path of the immersed portion of the movable electrode and in suitable proximity thereto.

5. IIn an' eleetrolytic cell, an electrode conl movable elec- A located farther bel sisting:r oi" a" rotary cylinder mounted on a horizontal axis, with its circumferential periphery mostly 'above, but having a lower segment dipping` into and only just below the surface'ot' the liquid electrolyte, in combination with a stationary electrode concentric to the segment of the rotary cylindrical electrode thus immersed, and located opposite and in suitable proximity thereto beneath the surface of the liquid electrolyte.

6. In an electrolytio cell, an electrode consisting of a rotary cylindrical cage mounted on a horizontal axis and having its circumferential periphery ons series of separate longitudinal bars, with most of this circumferential periphery above but-a lower segment thereof dipping into and only just below the surface of the liquid electrolyte, in combination with a. stationary electrode concentric to such immersed segment of the rotary cylindrical electrode and located opposite and in suitable proximity thereto beneath the surface of the liquidv electrolyte.

7. An clectrolytic cell, comprising a lateral extension curving outward and upward from the top of one of the sides of its main body and inclosed between its correspondingly extended ends; a stationary electrodeplate supported upon the inside of this curved extension and shaped to the segment of a cylinder; a rotary electrode consisting of a cylindrical cage mounted on a horizontal axis concentric to the curvature of the stationary electrode-plate and so -dimensioned that its circumferential periphery composed of a continuous series of longitudinal bars is brought into suitable proximity to such stationary electrode-plate; and

composed of a continuy such airarrangement of these constituents I that the liquid electrolyte when at its intended normal level in the electrolytie cell will cover the face of the stationary eleci trode in whole or in part and will simulytaneonsly Yimmerse just below its surface more or less of the circumferential periphf ery of the rotary electrode where this latter' is directly opposed to the face of the stationary electrode thus covered.

8. An electrolytic cell, comprising a lateral extension curving outward and upward from the top of one of the sides ot its main body and inclosed between its correspondlingly extended ends; stationary anodeplate supported upon the inside of this l curved extension and shaped lo the segment of a cylinder; a rotary cathode consisting l of a cylindrical cage mounted on a horizontal axis concentric to the curvature of the stationary anode-plate and so dimensioncd that its circumferential periphery composed of a continuous series ot' longitudinal bars is brought into close proximity to such staltionary anode-plate; and such an arrange- ]ment of these constituents that the liquid electrolyte when at its intended normal level in the electrolytic cell will cover the face of the stationaryl anode in whole or .in part, and will simultaneously immerse justl below its surface more or less ol the circumferential periphery ol the rotary cathode where this latter is directly opposed to the face of the stationary anode-plate thus cov ed DERICK S. HARTSI ORN. l ALAN A. CLAFLIN. l Vllitnesses: l Guo. L. Renners,

FLORENCE A. COLLINS. 

